Many serious accidents have happened when someone thought a machine or the power to it was safely off. "Lock-out tag-out" is a way to protect yourself and others by ensuring that machines remain completely, temporarily off. Without a lock-out tag-out system there is the possibility that a machine will unexpectedly start up, either because of stored energy which was not correctly released or through the actions of someone starting the process without realizing that it isn't safe to do so.
The lock-out tag-out standard requires that hazardous energy sources be "isolated and rendered inoperative" before maintenance or servicing work can begin. These energy sources include electrical (either active current or stored as in a capacitor), pneumatic, hydraulic, mechanical, thermal, chemical, and the force of gravity. It is important to remember all of the energy sources must be "isolated and rendered inoperative." Overlooking an energy source has proved fatal on several occasions.
OSHA requires three basic elements in a lock-out tag-out program. These are training, written procedures, and inspections. Training is required for two types of people; "authorized employees" and "affected employees." Authorized employees are people who do the maintenance or servicing work. They are the people who actually perform the lock-out tag-out. Affected employees are people who may be affected by or work near equipment which is locked or tagged out. Affected employees are not permitted to perform servicing or maintenance work which requires a lock-out or tag-out.
Written procedures detailing the lock-out tag-out procedure are required for equipment having two or more energy sources. Written procedures communicate important information to persons performing lock-out tag-out. They identify energy sources, provide step-by-step instruction for locking or tagging out energy sources, releasing stored energy, and verifying the equipment cannot be re-started after lockout is applied. Group lock-out tag-out procedures must also be clearly documented. Procedures must be kept up-to-date, and changes must be communicated to everyone who may possibly be affected by them. They are only useful if all the information they contain is correct.
Seven Basic Steps for Lock-out Tag-out
Think, plan and check.
- If you are in charge, think through the entire procedure.
- Identify all parts of any systems that need to be shut down.
- Determine what switches, equipment and people will be involved.
- Carefully plan how restarting will take place.
- Notify all those who need to know that a lock-out tag-out procedure is taking place.
- Identify all appropriate power sources, whether near or far from the job site.
- Include electrical circuits, hydraulic and pneumatic systems, spring energy and gravity systems.
- Disconnect electricity.
- Block movable parts.
- Release or block spring energy.
- Drain or bleed hydraulic and pneumatic lines.
- Lower suspended parts to rest positions.
Lock out all power sources.
- Use a lock designed only for this purpose.
- Each worker should have a personal lock.
Tag out all power sources and machines.
- Tag machine controls, pressure lines, starter switches and suspended parts.
- Tags should include your name, department, how to reach you, the date and time of tagging and the reason for the lockout.
Do a complete test.
- Double check all the steps above.
- Do a personal check.
- Push start buttons, test circuits and operate valves to test the system.
When It's Time To Restart
After the job is completed, follow the safety procedures you have set up for restart, removing only your own locks and tags. With all workers safe and equipment ready, it's time to turn on the power.
Lock-out Tag-out Resources
Example of a machine-specific written lock-out tag-out procedure from Wisconsin Department of Administration (Word version, download and customize)
CDC/NIOSH example program with sample training sheets and lock-out tag-out procedure format